20mmx110mm Dummy

In a box of miscellaneous ‘stuff’ acquired today at a little gun show in Johnstown, NY at the famous Pine Tree Rifle Club, I seem to have a 20mm x 108mm dummy round. No primer or primer pocket just a flat solid base. No head stamp marking. Projectile is steel with what appears to be an aluminum/white metal ‘fuse’ with the numbers; 1211649-1 stamped into it. A copper or bronze rifling band with the following marking; 20-mm MK11-0 A LOT HMC (this is a small font and inclosed in a box) 1-15. Projectile is very securely crimped in place. Case appears to have powder or a substitute filler( assume for weight simulation). As this is not my line of interest I really don’t have a clue what it is. But, I do find it a curiosity. What vintage and is it a proving dummy?

If it does not have a rebated rim (and being a 20x110RR Oerlikon then) it shounds much like a naval 20x110 USN for the MK12 aircraft gun.

Here a quick image:

Alex thank you. It appears to be the the same shape projectile and band and crimp style. This case is brass and the rim is not rebated.
I will take a couple of pics and post them. Thanks again.

The images did not display when I made my first posting here.
Someone more knowledgable may correct me but brass cases are not very common in this caliber. I think the one you got is a scarce one.

I hadn’t posted them at that time. Thank you for the reply and info!

I have not found anything in print but I have info on this dummy round from a Marine armorer that served with the 1st Marine Airwing in RVN with VMA 121 in 1967. They flew A4 E Skyhawks. They were armed with the MK 12 Colt autocannon. This Marine has several dummies with this same projectile and except for lot numbers on the bearing band have virtually the same markings. The projectile on this round should be completely brown in color and when observed under magnification there are traces of the original brown paint. Especially at the case mouth. The projectile in the identical specimen to this one in his collection/accumulation, had a printed/stamped in black “Dummy 1-6 LC - 63” marking just above the bearing band. Lake City 1963 ? The other specimens had steel cases with black phosphate coloring and 2 -4 holes drilled in the case and one with a tinned steel case. The same projectiles. These had primer pockets that were empty. He said the brass examples like this one and his, had an inert filler to duplicate weight. Apparently the MK12 cannon was prone to malfunctions during high speed maneuvers and during training or practice re-timing guns and clearing jams was a common time consumer of his. He called this a MK 5 AMC Dummy. This pictured round should have a brown colored projectile. For what it’s worth…

Sportclay, when we take all existing dummies in this caliber there are plenty of variations in case coatings and projectile colors. I am not sure now but there was once an article or a website which had plenty of the variations.

The dark phosphated case you mention could well be an Argentine one. Here an image:
mla-s2-p.mlstatic.com/malvinas-m … 2013-O.jpg

That certainly looks like one of the examples I saw. This is terrible, another collecting tangent I don’t need, but can’t resist…

There are a lot of variations to collect: cartrology.com/browse-ammuni … N&Country=